This looks like it was accidentally caught up in e21a05cb (doc:
cpuset: Update the cpuset flag file, 2010-02-24).

While I'm touching the line, also fix the posessive "cpusets" ->
"cpuset's".
Signed-off-by: NW. Trevor King <wking@tremily.us>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>